Hydraulically balanced valve system



Feb. 26, 1952 SEAMAN HYDRAULICALLY BALANCED VALVE SYSTEM 4 Sheets-Sheet1 Filed Sept. 7, 1946 //III/ Z 3 3nnentor #Mr/L J W 'M 5 57/ GttornegFeb. 26, 1952 Filed Sept. 7, 1946 H. SEAMAN HYDRAULICALLY BALANCED VALVESYSTEM 4 Sheets-Sheet 3 LIN E 0 CLOSE l80 OPEN 360 231 VALVE A VALVE B234 BY-PASS 226 Zmventor Q 5 (Ittorneg Feb. 26, 1952 SEAMANHYDRAULICALLY BALANCED VALVE SYSTEM 4 Sheets-Sheet 4 Filed Sept. 7, 1946EEiEE:

1 M l A I WIIII'IIII'IAIIIIII/ Zhmentor Bu fjww 6% (Ittomeg PatentedFeb. 26, 1952 HYDRAULICALLY BALANCED VALVE SYSTEM Henry Seaman, Canton,N. 0. Application September 7, 1946, Serial No. 695,359 Qlaims. (Cl.137-144) This invention relates to valves and fluid control devices andhas especial value'in control of flow at high pressure and/or in pipesof large diameter. In such cases the total pressure on one side of thevalve strongly resists'either the openingor closing, or both, of valvesof the usual types. In order to secure easier opening, so calledbalanced valves have been used in certain applications. These have notproven satisfactory for general application. It is difficult, forexample, to seat both discs, used in the usual balanced valves, withequal tightness, and because of the parallel arrangement of the twoparts of the valve a leak in either constitutes a leak in the valve.

The primary object of the present invention is to provide a valve whichcan be opened and closed with little effort, whether manual or by othersource of power, even when used with high pressures or made in largediameters. A further object is to provide a valve wherein pressures onopposite sides of the valve disc can be substantially balanced at thetime it must be moved by applied power against the flow of fluidtherethrough. Another object is to provide a valve which can be seatedtightly and held tight by the controlled pressure and can be unseatedand opened without the necessity of overcoming the said pressure. Astill further object is to provide novel and separate controls forthetwo elements of a balanced valve whereby the necessary condition ofbalance is maintained by differential operation of the two elements.Still another object is to provide a fluid control valve device whichcan be hydraulically operated by use of hydraulic pressures which aremuch lower than the controlled pressure and/or which operate inhydraulic cylinders much smaller than the diameter of the pressureretaining element of the valve. Yet another object is the provision ofsuitable hydraulic control mechanism for this purpose. Other objects andadvantage of the present invention will be apparent from the followingdescription.

I have found it possible to accomplish the aforesaid objects by usingvalves of the type wherein the movable element (hereinafter called discor plug-which terms are herein used synonymously) moves perpendicularlyto the seat, as in the well known globe, angle, and needle valves, asdistinguished from gate, piston, and sliding valves and cocks, whereinthe movable element moves parallel or nearly parallel to the seat. Forthe purposes of the present invention I install two such valves inseries so that the pressure of the controlled fluid tends to open oneand close the other. I further provide operative interconnectionsbetween these two valves whereby both the openin and the closingmovement of that valve disc which seats with the pressure of thecontrolled fluid, take place somewhat in advance of the correspondingmoverxient of the other valve disc, thus maintaining a substantialbalance between the pressures above and below the valve disc which ismoving in'opposition to the flow of the controlled fluid.

The invention will be furtherdescribed with reference to theaccompanying drawing in which:

Figure 1 is a diagrammatic illustration of one embodiment of the presentinvention.

Figure 2 is a diagrammatic illustration of a special multi-way controlcock to control the timing of the hydraulic operation of the valve.

' Figure 3 is a diagrammatic illustration of another embodiment of thepresent invention.

Figure 4 is a diagrammatic representation of a third embodiment of thepresent invention wherein the valves are solenoid operated.

Figure 5 is a diagrammatic representation of a fourth embodiment showingelectric motor operation of the valve.

Figure 6 is a timing diagram showing the timed operation of the switchesin the embodiment illustrated in Figure 5.

Figure 7 is a diagrammatic representation of still another embodimentwherein the valve device of the invention is arranged for manualoperation.

Figure 8 is a fragmentary sectional view of the master control cocktaken on line 88 of Figure 3, and showing the axial relationship of theopenings therein.

Referring first to the embodiment illustrated in Figure l, a primaryvalve A and auxiliary valve B are connected in series. The controlledfiu'id enters valve B through pipe 25, is conducted through passage (ormultiple passages if desired) to primary valve A, and leaves the devicethrough pipe 23. Valve A comprises a body 25, a stationary seat 25, anda movable disc 26 operated by sliding stein attached to piston 28 inhydraulic cylinder 29. lhe corresponding parts of valve B are designatedby numerals 34, 35, 35, at, 33, and 39, respectively.

'As is apparent from the drawing, the valves are so connected that thepressure of the controlled lluid aids the closing and resists theopening of valve A whereas it resists the closing and aids' the openingof valve 13.

Hydraulic fluid under pressure is supplied through a conduit 45 from anysuitable source. Its flow is controlled by three-way cocks AI and 42. Abranched conduit =33 connects cock ii to the spaces behind pistons 28and 38 in cylinders 29 and 39 respectively. In the branch leading tocylinder 39 is a swing check valve 44 adapted to pass fluid freely intocylinder 39 but permit its escape only very slowly through an orifice45. A branched conduit 46 connects cock 42 to the space before thepistons 28 and 35 in cylinders 29 and 39, respectively. In the branchleading to cylinder 29 is check valve 41 adapted to pass fluid freelyinto cylinder 29 but permit its escape only very slowly through anorifice 18. Cocks 4! and 42 are adapted to connect the conduits 53 and46 either to pressure conduit 35 or exhaust designated generally by thenumeral 55.

A by-pass 5|, 53 including stop cook 52 leads from passage 22 to thepipe 23 around valve A or may lead to waste or other space where thepressure approximately equals that in pipe 23.-

With the valve device (both valves A and B) open as illustrated inFigure l, the operation of closing the valve will first be described.Cocks 4| and 42 are turned to the positions shown in the figure whichadmits hydraulic fluid freely behind both pistons and permits freeexhaust from before piston 38 and exhaust at only a very restrictedrate, through orifice 48, from before piston 28.

Valve A is thereby closed slowly, without shock or water-hammer in spiteof the pressure of the controlled fluid on valve disc 25, due to theresistance imposed by orifice 48. The closing of valve B lags behindthat of valve A by an amount which is greater as the hydraulic pressureapplied through piston 38 is less, because of the balancing of thispressure against the pressure drop through valve B. When valve A iscompletely closed the pressure in passage 22 equals that in pipe 2| andvalve disc 36 is seated firmly by the hydraulic pressure on piston 38.

Both valves A and B are now closed and cooks 4| and 42 may be left inthe positions shown or turned to seal off conduits 43 and 45 so thathydraulic fluid can neither enter nor leave cylinders 29 and 39. Eventhough this should not keep valve B tightly closed, valve A will be heldclosed by the pressure of the controlled fluid and leakage cannot occur.

To open the valve device, three-way cook 42 is turned to connect conduit45 to pressure line 46, thus freely admitting hydraulic fluid tocylinders 29 and 39, in front of pistons 28 and 38. At the same timethree-way cock 4| is turned to connect conduit 43 to exhaust, whichpermits free exhaust from behind piston 28 and exhaust at only a veryrestricted rate, through orifice 45, from behind piston 38. Stop cock 52is also opened thus equalizing the pressures above and below valve disc26, which at that time is firmly seated on seat 25, this in spite of anyleakage which may exist between valve seat 35 and disc 36. Because ofthe balanced pressures above and below valve disc 26 and the freeadmission of hydraulic fluid before, and its free exhaust from behindpiston 28, valve A opens rapidly. At the same time valve B opens slowly,in spite of the pressure of fluid in pipe 2| on valve disc 35, due tothe resistance imposed by orifice 45. This slow opening of valve Bprevents pressure in passage 22 from building up to an extent whichwould interfere with the full and free opening of valve A. Both valvesare then fully open, as

-ated as a unit. It will be noted that direction will accomplish openingof the shown in the figure. The by-pass, if connected to pipe 23 asillustrated, may remain open without harm, but since it is only requiredto be open during the unseating of valve disc 26, I prefer to close cook52 during the early part of the valve opening operation. It then remainsclosed until just before the beginning of the next opening operation.

Three way cocks 4| and 42 and stop cook 52 have so far been described asindependently operated. Since proper synchronization of their operationis necessary to successful operation of my valve device, I prefer tohave them all operall three are illustrated in the position for closingthe valve, and that turning each of them simultaneously through-ninetydegrees in a clockwise valve, and that further turning through 270degrees in the same direction will return them to their illustratedvalve-closing positions without again opening the by-pass 5|, 52, 53.

The timed relationship between the operations of cocks 4|, 42, and 52can perhaps be better understood by reference to Figure 2 which showshow all may be replaced by a single multiway cock 55. In the positionillustrated hydrauli c fluid passes from pressure conduit 48 throughpassage 56 in cook 55 into conduit 43 which delivers it behind thepistons in cylinders 29 and 56 into conduit 46 and exhaust from conduit43- through passage 51 into conduit 56, to open the valve. All three areopen simultaneously for a brief interval to permit free unseating ofvalve disc 26, before cook 55 reaches the position indicated by brokenlines, where by-pass 5|-53 is again closed and passages 56 and 51 are inposition to complete opening of the valves. Con-' tinued clockwiserotation of cock 55 brings it to a position diametrically opposite thatshown in the figure and in all respect identical thereto each half turngiving a full cycle of opening and closing the valve. It may be notedthat passages 56 and 51 can pass the openings of by-pass conduits 5| and53 without connecting them, and that openings 58 and 59 can pass theopenings of conduits 46, 43, 46 and 56 without connecting them.

If it is desired to operate the valve in throttling position, the cooks4|, 42, 52 or the multi-way invention, wherein the positions of primaryand secondary valves A and B are the reverse of those illustrated inFigure 1. In this case the controlled fluid passe from pipe |2| throughvalve A, the passage I22, and valve B into pipe |23. Valve A comprisesseat I25, disc I26, and stem accuses 5. I21, connected to piston I28 incylinder I29. Similarly valve B comprisesseat I35, disc I36, and stem I3connected to piston I38 in cylinder I39. A by-pass II, I52, I53 aroundvalve A is also provided as in Figure 1.

In Figure 3 there is also illustrated a modified system or" hydrauliconnections and controls for operating the valves. it is to beunderstood, however, that the hydraulic connections illustrated inFigures 1 and 2 can be applied to the valve arrangement illustrated inFigure 3 and vice versa. In the system illustrated in this figure theorifice check valves are replaced by orifices permanently fixed in thedischarge pipe lines as hereinafter fully explained.

Hydraulic fiuid under pressure is, in Figure 3,

supplied through conduit I48 controlled by a special cock MI. A conduitI='i3 connects the space behind piston I28 in cylinder I29 to cook I II.A conduit I 45 connects the space behind piston I 33 in cylinder I39directly to one position on the periphery of cock l II and through apermanent constriction or orifice M5 to another position on saidperiphery. Similarly a conduit I45 connects the space in front of pistonI38 in cylinder I39 to cook Id A conduit I4? connects the space in frontoi piston I28 in cylinder I28 directly to one position on the peripheryof cock I4! and through a permanent constriction or orifice I43 toanother position on said periphery.

With the apparatus as described, the operation is analogous to thatdescribed with reference to Figure 1. To close the valves cock I ii isturned to the position shown diagrammatically in Fig ure 3. This admitshydraulic fluid freely behind both pistons (orifice connection M5 beingclosed by cock I lI and permits free exhaust from before piston I38 incylinder I39, and exhaust at only a very restricted rate, throughorifice I IS, from the space before piston I in cylinder I29 (freeconnection from conduit I47 to exhaust being closed by cock l il Valve Ais thereby closed slowly without shock or water-hammer, in spite of thepressure of the controlled fluid on valve disc I26, due to theresistance imposed by orifice I48. The closing of valve B lags behindthat of valve A by an amount which is greater as the hydraulic pressureapplied through piston I38 is less, because of the balancing of thispressure against the pressure drop through valve B. When valve A iscompletely closed valve B is not yet closed because of this lag. Thepressure in passage I22 is then equal to that in pipe I23 and valve discI is seated firmly by the hydraulic pressure on piston I35.

Both valves A and B are then closed and cock I4I may be left in theposition shown or turned in a clockwise direction for about degrees,closing oil both the pressure and exhaust conduits and separatelysealing off the pressures before and behind the pistons. Even thoughthis should not keep valve B tightly closed, valve A will be held closedby the pressure of the controlled fluid and leakage cannot occur.

- To open the valve, cock I 4I is turned in a clockwise direction forabout one fourth turn to the position indicated by broken lines inFigure 3. This admits hydraulic fluid freely in front of both pistons(orifice connection I48 being closed by cock MI) and permits freeexhaust from be hind piston I28 in cylinder I29, and exhaust at only avery restricted rate from behind piston I38 in cylinder I35 throughorifice I45 (free connection from conduit hi4 to exhaust being closedby'cock'MI') broken lines in Figure 3 the opening I52 passes trated in apurely diagrammatic manner and openings into conduits I 5i and IE3temporarily completing the by-pass around valve disc I25 and equalizingthe pressure on opposite sides thereof. As in the embodiment illustratedin Figures 1 and 2, this by-pass remains open until the cock I lI hasopened conduit I42 to pressure and I 13 to exhaust, thus unseating valveI26 before the bypass is closed by turning cook to the positionindicated by broken lines and bringing opening I52 to the position shownin the figure by dot-and-dash lines designated I52. Because of thebalanced pressures above low valve disc I25 and the free admission ofhydraulic fluid in front of, and its free exhaust from behind pistonI28, valve A opens rapidly. At the same time valve B opens slowly, inspite of pressure of fluid in passage I22 on valve disc I38, due to theresistance imposed by orifice I45. This retarded opening of valve Bmaintains in passage I22 sumcient pressure to nearly balance thepressure above valve disc I25 and thus permit the full and free openingof valve A.

Both valve A and B are then fully open as shown in the figure. By-passI5I-I52I53 is closed, though, when connected directly from pipe iii topassage I22 as shown, the opening I52 through cock I lI may be locatedto leave the b'y-pass open so long as cock I lI remains in thevalve-opening position, and to close it as soon as the cock is turned tothe valve-holding or valve-closing position.

Instead of the single, three way or multi-way cocks, other types ofvalves can be used if desired and correct timing secured by interlocksor cam operation as will be well understood by those skilled in the art.

While I prefer the hydraulic operation of my improved duplex valvedevice, it is possible to secure many advantages of the presentinvention while using electric, mechanical, or even manual operation.

Solenoid operation is possible on valves that are not too large. Suchoperation is illustrated in Figure a wherein valves A and B areillusarranged exactly as in Figure 3. Valve A pulled open by core I5I ofsolenoid I52 against the action of spring I53, which serves to closevalve A when the solenoid lot? is deene The opening action is unimpededbut the clos action is retarded to the desired degree by way dash potI54 the piston of which moves freely to the left but meets theresistance of entrapped fiuid in moving to the right. Valve B issimilarly opened by core III in solenoid Il2 against the action ofspring II3. Qpening of valve 13 is retarded by one way dash pot M4, thepiston of which moves freely to the left but meets the resistance ofentrapped fluid in moving to the right, while the closing action of thevalve is unimpeded. By-pass ISI, I82, I53 is similar to that describedwith reference to Figure 3 but is operated by solenoid I84 and springI85. Sole- 7 holds !62, I12 and I84 are connected in parallel so thatall are energized and de-energized simultaneously. The action of thevalve is clearly identical with that already described except thatby-pass !6!, I82, !63 is open so long as the valves are open. This isnot significant but could be changed in a known manner if desired. Withthe arrangement shown the valve is open so long as the solenoids areenergized and closed while they are de-energized.

Alternativeelectric motor operation is illustrated in Figs. and 6. Inthis modification valve A is operated .by screw through gearing 262, bymotor 263. A collar 204 on screw 20! operates to open limit switches 265and 266 to stop further operation of motor 263 when the valve hasreached the limit of its motion. Similarly valve B is operated by screw2! through gearing 2I2, by motor 2!3, and a collar 2!4 on screw 2!!operates limit switches H5 and 2!6.

By-pass 22!, 223, being small, is preferably opened through valve 222 bysolenoid 224 and closed by spring 225'. The operation of the by-passvalve is controlled by a switch 226 as hereinafter described. Operationof the motors may be initiated by any suitable switching device such asa drum switch, or cam operated switches, such as are indicateddiagrammatically at 23!, 232, 233, and 234. The cam or drum whichcontrols the timing of the operations is illustrated diagrammatically inFigure 6. The first 180 deg. of rotation control the closing and thesecond 180 deg. control the opening of the valve. The lines in thefigure are numbered to indicate the switch controlled thereby. Thehigher portions of each line indicate the time the switch is open andthe lower portion the time when the switch is closed. It will beapparent from the figure that if the cam or drum be rotated at a uniformand suitably slow rate for 180 deg. at a time, always in the samedirection, theoperation of the valve device will be the same aspreviously described. The speed of rotation should be such that themovement of each of the valves is completed before the switch initiatingthe operation is again opened. Rotation of the drum switch isadvantageously accomplished by a small electric motor which can bestarted by a push button and stopped by completion of 180 deg. movementof the drum. By this means the valve device can be completely operatedin opposite directions successively by a single push button, a singlepressure on the button for each operation.

With the described timing of the valve operation, the only movementwhich must take place under seriously unbalanced pressure is movement inthe direction of fluid flow. Movement of the valve disc, even in thisdirection requires unduly great moving force with the usual screw stems.I accordingly prefer to provide screw stems having thread angles almostlarge enough for the pressure on the disc to cause rotation of thescrew, using double or higher multiple threads as necessary for thispurpose. The fluid flow then assists movement in this direction whilethe balanced pressures permit free movement in the other direction. Thepower required to operate this valve is accordingly very small in spiteof high pressures or large valve openings.

It is also possible to adapt my duplex valve to manual operation byusing suitable interlocks to insure proper timing of the operations. Onearrangement of parts for this purpose is diagrammatically illustrated inFigure '1. In the specific embodiment of my invention illustrated toshow the application of manual operating devices, the

controlled fluid enters through pipe 25!, passes through valve B,passage 252, and valve A, and leaves through pipe 253. Movable disc 256of valve A is operated by threaded stem 251 which is turned in threadednut 258, fixed to the valve structure, by means of hand wheel 259. Thecorresponding parts of valve B are designated by numerals 266, 261, 268,and 269 respectively.

For the purpose of controlling the sequence of operation of valves A andB, the valve stems are provided with portions 216 and 21 I,respectively, of enlarged diameter. To prevent attempted closing ofvalve B before the required closing of valve A, if the fluid pressureitself is not adequate, a

detent 212 pivoted at 213 to the valve structure can be provided. Asshown it is adapted to be held by a spring 214 under enlargement 21! onstem 261 and prevent any closing of valve B. When valve A is closedsufficiently, enlargement 216 on the stem 251 of valve A contacts arm215 on detent 212 and rocks it out of the path of enlargement 21! andthereby permits closing of valve B by turning hand wheel 269.

To prevent premature opening of valve B and admission of the linepressure into passage 252, which would impose almost if not quiteprohibitive resistance to the opening of valve A, a detent 262 isprovided. This is mounted to rock on fixed pivot 263 and is normallyheld, by spring 284, in the path of enlargement 21! on stem 261 of valveB when this valve is closed. Valve B being closed, valve A can be openedreadily because of the balanced pressures above and below disc 256.

. When valve A reaches the desired opening, as

illustrated in the drawing, contact of enlarge ment 216 on valve stem251, with arm 285 on detent 262 has rocked the detent to the positionshown in the drawing, out of the path of enlargement 21! on valve stem261, to permit opening of valve B, which opening is facilitated by thepressure of the controlled fluid below disc 266.

By-pass 29!, 262, 293 around disc 256 of valve A, is provided as and forthe purposes hereinbefore described. Cock 292 which controls thetransmission of pressure through the by-pass can be operated, by handle293, movement of which is limited by fixed stops 294. The fluid pressureitself is adequate to require opening of the by-pass (unless suchopening is unnecessary) before opening of valve A. It is necessary,however, to be certain that cock 292 is closed at least by the timevalve A is again fully closed. This can conveniently be accomplished bythe final portion of the opening action, since there is no need for theby-pass to be open after the valve A has been even partially opened. Forthis purpose arm 295 may be provided on the movable plug of cock 292. Asvalve A is opened, enlargement 216 on stem 251 contacts arm 295 androcks cock 292 to the closed position, where it remains until it isagain opened preparatory to the next opening of the valve.

For satisfactory manual operation the thread angle must also be large,for the reasons set forth in connection with the description of electricoperation.

It will be evident that the operation of this embodiment of theinvention is essentially the same, except for the motive power employed,as the operation of the other embodiments described.

The mechanism illustrated in the drawings is all shown diagrammatically.No attempt has been made to show actual more or less conven-- tionaldetails of construction such as packing boxes, screwed and flangedjoints, etc., since these can be readily supplied. by those skilled inthe art after the principles of the present invention are understood.

The present invention has been illustrated in various embodiments andwith various operating media. However, all involve the duplex principlewith two valve elements closing in opposite directions relative to thedirection of flow of the controlled fluid, and the control of theoperation of the element which moves in the direction of fluid flowtogether with a by-pass valve to maintain substantially balancedpressure on the other element so that it can operate freely. Variousother changes can be made by those skilled in j the art withoutdeparting from the invention as described and claimed. As will beunderstood by those skilled in the art, each of the various embodimentsand operating media is better than the valve operated thereby.

I claim:

1. In combination: a primary fluid control valve comprising a stationaryseat and a disc movable perpendicularly thereto so that pressure of thecontrolled fluid aids seating and resists unseating of said disc; anauxiliary valve similar to and in series with said primary valve butseat ing in the reverse direction so that pressure of I the controlledfluid resists seating and aids unseating of the disc: means for openingand closing both of said valves; and means for reducing the forcereouired for opening said primary valve,

which comprises means for equali'zing the p essure on opposite sides ofsaid primary valve disc before said valve is to be opened; and means formaintaining nearly balanced pressure on opposite sides of said primaryvalve disc dur: ing opening thereof, said balanced pressure maintainingmeans comprising unidirectional retarding means for preventing thedegree of opening of said auxiliary valve from exceeding that of primaryvalve at any time throughout the opening operation.

2. In combination: a fluid control valve comprising a stationary seatand a disc movable perpendicularly thereto so that pressure of thecontrolled fluid aids seating and resists unseating of said disc: anauxiliary valve similar to and in series with said first named valve butseating in the reverse direction so that pressure of the controlledfluid resists seatin and aids unseating of the auxiliary valve disc; ahydraulic cylinder and piston operatively connected to said first namedvalve disc; a hydraulic cylinder and piston operatively connected tosaid auxiliary valve disc; inlet means for admitting hydra lic fluidfreely to each side of each piston; outlet means for freely releasinghydraulic fluid from that side of each piston which permits movement ofthe corresponding valve disc in a direction opposite to the flow of thecontrolled fluid; and outlet means of much smaller capacity forreleasing hydraulic fluid at a restricted rate from 10 that side of eachpiston which permits movement of the corresponding disc in the directionof flow of the controlled fluid.

3. In combination: a fluid control valve comprising a stationary seatand. a disc movable perpendicularly thereto so that pressure of thecontrolled fluid aids seating and resists unseating of said disc; anauxiliary valve similar to and in series with said first named valve butseating in the reverse direction so that pressure of the controlledfluid resists seating and aids unseating of the auxiliary valve disc; ahydraulic cylinder and piston operatively connected to said first namedvalve disc; a hydraulic cylinder and piston operatively connected tosaid auxiliary valve disc; inlet means for admitting hydraulic fluidfreely to each side of each piston; outlet means for freely releasinghydraulic fluid from that side of each piston which permits movement ofthe corresponding valve disc in a direction opposite to the flow of thecontrolled fluid; means of much smaller capacity for releasing hydraulicfluid at a restricted rate from that side of each piston which permitsmovement of the corresponding disc in the direction of flow of thecontrolled fluid; and means for controllin admission and release ofhydraulic fluid to and from both cylinders in such relation to thepistons that both valves are simultaneously urged in the direction toopen or close both valves, as desired.

4. A balanced valve structure comprising, a primary valve and anauxiliary valve, connected in series, each comprising a stationary seatand a movable disc so arran ed that to close both valves the discs aremoved in opposite directions, relative to the direction of fluid flowtherethrouch, the primary valve disc moving in the direction of saidfluid flow and the auxiliary valve disc moving counter thereto; meansfor moving both discs to open or close both valves; unidirectionalretarding means separately associated with each of said valve discs.each operative to retard the motion of the associated disc in the diection of flow through the alve.

5. A balanced valve structure comprising, a primary valve and anauxiliary valve, connected in series, each comprising a stationary seatand a movable disc so arranged that to close both valves the discs aremoved in opposite directions, relative to the direction of fluid flowtherethrough, the primary valve disc moving in the direction of saidfluid flow and the auxiliary valve disc moving cornter thereto; meansfor moving both discs to open or close both valves; retardin meansoperati e during the closing action for preventing excessively rap-idclosing of said primary valve; means for equalizing the pressure on oposite sides or" said primary valve disc before starting to open eitherof said valves; and means operative during the open ng action forretarding the openin of the auxiliary valve to prevent a substantialunbalance between the fluid pressures on opposite sides of said primaryvalve disc such as would interfere with the free opening thereof.

6. A balanced valve structure comprising, a primary valve and anauxiliary valve, connected in series, each comprising a stationary seatand a movable disc so arranged that to close both val es the discs aremoved in opposite directions relative to the direction of fluid f owtherethrough; a hydraulic cylinder and piston operatively connected witheach of said valves for controlling the flow of fluid therethrough, theprimary valve disc moving in the direction of said fluid flow and theauxiliary valve disc moving counter thereto; a by-pass connecting thespace between said valves with a space wherein the pressure approximatesthat on the other side of said primary valve disc; valve means in saidbypass for controllin the transmission of pressure therethrough; valvemeans for controlling admission of pressure fluid to, and escape ofressure fluid from, each side of both of said hydraulic cylinders;interconnections between said valve means for controlling the sequenceof the operations thereof, to open said by-pass preliminarily to theadmission of pressure fluid into said hydraulic cylinders to open saidprimary and auxiliary valves, and to close said by-pass preliminarily toadmission of pressure fluid into said hydraulic cylinders to close saidprimary and auxiliary valves.

'7. In combination: a primary fluid control valve comprising astationary seat and a disc movable perpendicularly thereto so thatpressure of the controlled fluid aids in seating and resists unseatingof said disc; an auxiliary valve simi-.

' lar to and in series with said first named valve but seating inreverse direction so that pressure of the controlled fluid resistsseating and aids unseating of the disc of the auxiliary valve; ahydraulic cylinder and piston operatively connected to said primaryvalve disc; a hydraulic cylinder and piston operatively connected tosaid auxiliary valve disc; a fluid by-pass connecting the space betweensaid valve discs with a space wherein the pressure approximates thepressure on the other side of the primary valve disc; means foradmitting hydraulic fluid to and taneously freely admitting hydraulicfluid to both of said cylinders for closing both said primary valve andsaid auxiliary valve, and permitting free escape of hydraulic fluid fromthe other side of the piston which is closing said auxiliary valve andonly restricted escape, through one of said constrictions, of hydraulicfluid from the other side of the piston which is closing said primaryvalve, said valve means being' further operable to open said by-pass,and to simultaneously freely admit hydraulic fluid to both of saidcylinders for opening both said primary valve and said auxiliary valvewhile permitting free escape of hydraulic fluid from the other side ofthe piston which is opening said primary valve and only restrictedescape, through one of said constrictions, of hydraulic fluid from theother side of the piston which is opening said auxiliary valve, and,after admission of fluid to said cylinders, to again close said by-pass.

8. In combination: a primary fluid control valve-comprising a stationaryseat and a disc movable perpendicularly thereto 50 that pressure of thecontrolled fluid aids seating and resists unseating of said disc; anauxiliary valve similar to and in series with said first named valve butseating in reverse direction so that pressure of the controlled fluidresists seating and aids unseatin of the disc of the auxiliary valve;means for closing said primary valve slowly to avoid shock; means forclosing said auxiliary valve following slightly behind the closing ofsaid primary valve; means for equalizing the pressure on opposite sidesof said primary valve prior to opening said valve; means for openingsaid primary valve; and means for opening said auxiliary valve followingsomewhat behind the opening of said primary valve, whereby the pressureson opposite sides of said primary valve disc are maintainedsubstantially balanced during the opening thereof.

9. Method of operating a valve which closes with and opens against thecontrolled pressure by use of forces much less than those due topressure of the controlled fluid, which comprises: closing the fluidpassage near the valve before the valve is to be opened; substantiallyequalizing the pressure between the valve and said closure with that onthe other side of said valve; openin said valve; reopening the fluidpassage near the valve in such a manner as to cause said reopeningaction to lag behind the opening of the valve to an extent to maintain anear balance between the pressures above and below said valve.

10. Method of operating a valve which closes with and opens against thecontrolled pressure by use of forces much less than those due topressure of the controlled fluid, which comprises: closing the valve;constraining the closing action to take place slowly; closing the fluidpassage near said valve in such a manner as to cause said closing actionto lag behind the closing of the valve to such a degree that at leastthe major portion of the pressure drop caused by cutting oif the fluidflow takes place at the valve itself; then, prior to opening the valve,substantially balancing the pressure on opposite sides of the valve;opening the valve; openin the closure made near the valve in such amanner as to cause said opening action to lag behind the opening ofthe'valve so that not more than a minor portion of the total pressuredrop due to restricted flow, takes place at the valve during openingthereof.

HENRY SEAMAN.

REFERENCES CITED The following references are of record in th flle ofthis patent:

UNITED STATES PATENTS Number Name Date 1,169,401 Hodgson Jan. 25, 19161,290,722 Doble Jan. 7, 1919 1,394,332 Myer Oct. 18, 1921 1,838,723Welcker Dec. 29, 1931 1,861,742 Hand June 7, 1932 2,085,893 Boland July6, 193'? FOREIGN PATENTS Number Country Date 363,89? Italy Oct. 17, 1938

